I have a Garmin Nuvu sat-nav. Works very well in the air although I can't load the CAA chart. But you can see names of towns, roads etc. You can zoom out to a suitable scale and the map doesn't try and zoom in again like it does when you're driving a route.
As my main nav tool I print out the Memory Map CAA charts to a bigger scale and put them in a plastic folder display file in the order in which I am flying. (Using the laminated CAA charts I tend to take 2 - 3 seconds just finding the part of the chart I need - very frustrating).